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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5626_Библиотеки_им_академика_М_И_Перельмана.pdf
Flow of citrus peels
Perforation to collect oil mixture
Peel waste
Figure 7.8 Schematic representation of ecuelle extraction. Source: Kalaskar MG.
shell, facilitated by a slowly moving Archimedean screw.
The surface of this screw meticulously scrapes the surfaces
of the fruits, inducing the bursting of some essential oil
cavities on the peel. The released oil–water emulsion is then
brought forth. Subsequently, the screw conveys the treated
fruits into a hopper, where rollers, adorned with abrasive
spikes, rupture the remaining oil cavities. A gentle mist of
water is applied to rinse away the oil and water emulsion
from the fruit. The emulsion then passes through a separator where any solids are removed (Figure 7.8). Following
this, the pure oil is separated using a centrifuge [16, 17].
7. 6 Methods of Extraction 131
Citrus peels
Wooden frame
Petals of ower
Fat smeared on glass plate
7.6.5.4 Enfleurage
This process is employed for the extraction of the most
refined perfume oils, particularly from natural flower oils,
wherein the biosynthesis of essential oils continues even
after plucking the flowers. The extraction procedure
involves layering a mixture of melted beef tallow and lard
onto both surfaces of individual glass plates enclosed
within a wooden frame, forming a chassis. Each glass plate
is generously sprinkled with flowers, effectively covering its
surface. In this configuration, each layer of flowers becomes
enclosed between two layers of fat. These plate assemblies
are left undisturbed for a period of 24 hours. Following this,
the flowers are removed and replaced with a fresh supply
(Figure 7.9). This cycle is repeated until the fat reaches saturation with the essential oil from the flowers or attains a
specific concentration. For jasmine flowers, this entire
enfleurage process spans a duration of 70 days. Subsequently,
the flowers are removed (defleurage), and the fat is isolated
and mixed with absolute alcohol. The volatile oil is extracted
by the alcohol, as it is insoluble in it, separating from the
fat. The resulting alcoholic extract undergoes careful cooling and filtration to eliminate any residual fat that might
remain in solution or suspension. To obtain the volatile oil,
Figure 7.9 Schematic representation enfleurage. Source:
Kalaskar MG.
three successive extractions using alcohol are conducted. If
the volatile oil is desired, fractional distillation or vacuum
evaporation at 0 °C is employed. Alternatively, the alcoholic extract can be diluted with water and saturated with
sodium chloride, causing the oil to separate while retaining
the fragrance of the fresh flowers [16, 17].
7.6.5.5 Hot Maceration Process/Digestion
This method involves the extraction of essential oils utilizing fats, albeit at higher temperatures. The process entails
immersing flower petals in molten fat heated to temperatures between 45 and 60 °C for a duration of 1–2 hours,
dependent on the specific plant species (Figure 7.10). The
same fat is reused successively with fresh batches of petals.
After each soaking, the fat undergoes filtration and is separated from the petals. Following 10–20 immersions, the fat
is separated from the spent petals and any residual water.
The absolute from the soaking process is then obtained
132 7 Methods of Extraction
Fat mixture
Flower
Heat source
Figure 7.10 Schematic representation of hot maceration for
extraction of essential oil. Source: Kalaskar MG.
from the fat, which contains the oil, through extraction and
concentration under low pressure. This method is particularly suited for highly delicate essential oil-containing
flowers, such as the lily of the valley, whose physiological
properties degrade rapidly after harvesting. Notably, this
extraction process significantly reduces the time required
compared to the extended duration of the enfleurage process [16].
7.6.5.6 Pneumatic Method
This process, analogous in principle to the enfleurage
method, involves the circulation of a warm air current
through the flowers. The air, laden with suspended volatile
oil, subsequently passes through a chamber where a fine
mist of melted fat is sprayed, facilitating the dissolution
and absorption of the volatile oil. The fat saturated with
essential oil is collected in a tray at the bottom of the pneumatic chamber (Figure 7.11). Essential oil is recovered
using solvents [21].
7.6.6 Phytonics
This newer extraction method employs a group of chemicals derived from non-chlorinated fluoro-hydrocarbons to
extract phytochemicals from medicinal plants. This inno-
vative technique was developed by Advanced Phytonics
Limited, based in Manchester, United Kingdom, and is
commonly referred to as Florasol Extraction. The unique
characteristics of these fluorocarbon solvents, which are
devoid of chlorine and represent the latest generation in
their category, have been effectively utilized in the extraction of botanical substances. The primary constituent of
this solvent is 1,1,2,2-tetrafluoroethane, commonly recognized as hydrofluorocarbon-134a (HFC-134a). Notably,
this solvent possesses a boiling point of −25 °C. Importantly,
it is non-flammable and non-toxic, setting it apart from
chlorofluorocarbons. Moreover, it does not contribute to
ozone layer depletion. At ambient temperature, it maintains a vapor pressure of 5.6 bar.
The equipment utilized in the phytonic procedure
includes a stirred extraction vessel or an extraction column, a vessel for evaporation and collection, a gas compressor, and a heat exchanger. The process involves the
evaporation of phytosol using the assistance of a gas
compressor, subsequent re-liquefaction, and passage via
the medium, which may take the form of either a stirred
batch or a packed column. Phytosol, enhanced with the
intended substance (or impurity), flows through a builtin filter into the evaporation chamber. Continuous operation of the extraction is achieved by recirculating the
phytosol, thereby requiring only a small inventory.
Enhancements in efficiency can be realized through a
multi-vessel design. Employing modified solvents, such
as HFC-134a, allows for highly selective extraction of
specific classes of phytoconstituents. Alternatively, other
modified solvents broaden the spectrum of extracted
components. Once the extraction process concludes, the
phytosol flow is redirected into a storage cylinder, and
the recovered material is obtained from the evaporator
(Figure 7.12). Notably, biological products resulting from
this process exhibit exceedingly low residual solvent levels. Residuals consistently measure below 20 ppm and
Hot air with essential oil vapours
Fine mist
Perforated
Tray
Hot Air
Pump
Hot Air ow
Figure 7.11 Schematic representation of pneumatic extraction of essential oil. Source: Kalaskar MG.
Flowers
fat
Pomade
Pump
Molten fat
7. 6 Methods of Extraction 133
Phytosol recovery valve
R
Extract
Tank
Phytosol
storage
tank
T
Temperature
exchanger
Figure 7.12 Schematic presentation of phytonic process.
Source: Richter et al, 1996.
P
Pressure
gauge
Phytosol
evaporating
tank
Product
often fall below detectable limits. These solvents possess
neither acidic nor alkaline properties, thus exerting minimal reactive effects on botanical materials. This process
mainly yields two types of products: firstly, the aromatic
components responsible for the fragrance of essential
oils, and secondly, bioactive extracts derived from plants
that can be used directly without any additional processing, either physical or chemical [22]. Moreover, waste
biomass from these plants is dry and deemed environmentally friendly for handling.
The phytonics technique is widely employed in highquality pharmaceutical-grade extracts from food, beverages,
flavored oils, and pharmaceuticals, including antibiotics.
Additionally, it refines raw materials from other extraction
methods, ensuring purity by reducing impurities like wax.
Furthermore, the waste biomass generated by these plants
possesses the advantageous properties of dryness and environmental sustainability when handled [23].
7.6.7 Pressurized Liquid Extraction/Accelerated Solvent Extraction
This method is acknowledged by several terms, including
pressurized fluid extraction (PFE), accelerated solvent
extraction, pressurized solvent extraction (PSE), or
enhanced solvent extraction system (ESE). PLE was introduced by the Dionex Corporation in 1995 as a modern
alternative to conventional techniques like maceration,
percolation, sonication, and Soxhlet extraction. It offers an
automated strategy for extracting solid samples utilizing
liquid solvents, whether aqueous or organic, either individually or in combinations, surpassing their boiling
points. This approach incorporates elevated pressures
ranging from 4 to 12 MPa and moderate-to-high temperatures spanning from 50 to 300 °C [24].
Standard parameters influencing the PLE process
include sample size, solvent type, pressure, temperature,
pH, flow rate, and extraction time. Among these, temperature and solvent type hold significant influence [25]. An
elevation in temperature reduces the viscosity and surface
tension while increasing the solvent’s solubility capacity.
Consequently, the mass transfer rate escalates accordingly
[26]. The PLE method employs minimal solvent quantities
due to its operational conditions, reliant on higher pressure
and temperatures. Consequently, the required extraction
time is notably reduced compared to alternative techniques, ensuring faster extraction [27].
In this process, a small volume of sample and solvent is
kept in a cartridge for a brief duration (5–10 minutes). To
transfer the sample extract from the extraction cell into a
collector flask, pressurized gas is utilized (see Figure
7.13) [24].
This method offers distinct advantages, such as expedited extraction within a time frame of 15−50 minutes, a
reduced amount of solvents (ranging from 15 to 40 mL),
and the elimination of the necessity for filtration. However,
the main drawbacks revolve around the requirement for
expensive equipment and the necessity for comprehensive
optimization of variables to prevent efficiency dependency
on the matrix [27].
PLE has proven to be a successful method for extracting
therapeutically active phytochemicals, including isoflavones and anthocyanins, from a diverse range of botanical
sources, such as freeze-dried soybeans, spinach, and even
marine sources [27−29]. Espada-Bellido et al. extensively
investigated the operational parameters of PLE, focusing
on crucial factors, such as solvent type, temperature, pressure, purge time, pH, and flushing. The specific focus was
on the extraction of anthocyanins and phenolic compounds from black mulberries. Through rigorous experimentation and statistical analyses, they deduced that
temperature and solvent composition played pivotal roles
in the extraction process. The optimal conditions for
extracting anthocyanins and phenolics were identified as
47.2 and 74.6% methanol in water, temperatures of 75.5
and 99.4 °C, pressures of 200 and 100 atm, a purge time of
90 seconds, pH values of 3.01 and 7, and flushing rates of
50.2 and 100%, respectively. A comparative analysis
between PLE and UAE methodologies demonstrated comparable extraction yields for anthocyanins. However, PLE
134 7 Methods of Extraction
Manometer
Pressure
vessel
Tank
Figure 7.13 Schematic presentation of pressurized liquid extraction [24]. Source: Kalaskar MG.
exhibited a notable advantage by necessitating lower solvent consumption. Furthermore, PLE displayed enhanced
extraction efficiency for total phenolic compounds when
contrasted with UAE. Consequently, PLE stands out as a
Valve
Pump
Extraction
cell with
Oven
the generator. UAPLE demonstrated itself as an efficient
alternative extraction method due to its substantial potential for enhancing phenolic compound extraction from
pomegranate peels.
Back pressure
lters
viable and efficient alternative method for the extraction
of bioactive compounds from mulberries [30]. Sumere
et al. assessed the combined approach of ultrasound and
pressurized liquid extraction (UAPLE) for extracting phenolic compounds from pomegranate peels [31]. They
investigated the influence of various solvents (water and
ethanol-water mixtures at different proportions), ultrasound power, average particle size of the plant material,
and temperature on extraction yield. Their findings highlighted that optimal extraction temperatures for phenolic
compounds using water ranged from 70 to 80 °C. However,
at 100 °C, the extraction yield decreased, possibly due to
the potential degradation of phenolic compounds at elevated temperatures. The study concluded that higher
yields could be achieved with larger particles and intermediate ultrasound power within the range of 480–640 W at
7.6.8 Pulsed Electric Field Extraction
PEF extraction is a non-thermal technology used to extract
bioactive compounds from biological materials, including
herbs and many more biological materials. It involves applying high-voltage pulses with an electric field intensity of
10–60 kV/cm for a short period as 1–300 μs, to the material
placed between two electrodes. These pulses generate an
electric field that permeates the cell membranes, inducing
temporary pores or openings, allowing the extraction of
intracellular compounds. The high electric pulses create temporary pores that cause structural changes in the cell membranes resulting in disruption of cellular integrity. This
disruption releases the cellular content from inside of the cell
to outside, facilitating the extraction process (Figure 7.14).
regulator
Collector
ask
Pulse generator
Pump
Treatment chamber
Temp exchanger
Raw
material
Figure 7.14 Schematic presentation of pulse electric extraction. Source: Kalaskar MG.
Monitor system
Electrodes
Cooling
chamber
Treated
material
7. 6 Methods of Extraction 135
The size-reduced plant material is placed between the
electrodes, and short pulses of high electric field intensity for a short duration are applied. The frequency and
number of pulses can vary depending on the material
and desired outcome. Parameters such as field strength,
specific energy input, pulse number, temperature, and
the matrix affect the efficiency of the process [32]. The
applied electric pulses create temporary pores, allowing
the extraction of intracellular compounds [33]. After
treatment, the extracted material is separated from the
solvent or carrier medium. Further processing like filtration or centrifugation may be required to obtain the
desired extract. This is an alternative method for heatsensitive bioactive compounds [32, 33].
Leong et al. in 2016 studied the extraction of anthocyanins from grape juices by application of PEF. The experimental conditions encompassed a pulse length of 20 ms, a
frequency of 50 Hz, and an electric-powered discipline electricity of 1.5 kV/cm. Observations indicated that PEF treatment augmented the efficacy of extracting anthocyanins,
nutrition C, and other bioactive compounds, simultaneously enhancing antioxidant activity [34]. Furthermore, it
became observed that PEF exhibited a protective impact on
cells, mitigating oxidative stress. Martinez and his colleagues successfully applied PEF treatment to extract carotenoids from fresh biomass using ethanol as solvent. The
operational parameters utilized were 15 kV/s and 150 μs.
The findings suggest that PEF presents itself as a viable
alternative to traditional methodologies [33]. Rodendo et al.
explored the utilization of PEF treatment to extract phenols, flavonoids, and antioxidant compounds from freshly
thinned peaches, aiming to reduce the necessary quantity
of methanol as an extraction solvent. Upon substituting
methanol with water and implementing PEF as an extraction aid, researchers noted a significant augmentation in
the levels of total bioactive compounds. Moreover, the concentrations of individual phenols, such as chlorogenic acid,
coumaric acid, and neochlorogenic acid, were observed to
increase in the resultant extract [35].
7.6.9 Ultrasound-assisted Extraction
UAE entails the application of high-frequency sound
waves, specifically ultrasound with frequencies ranging
from 20 to 2000 kHz, to expedite the extraction of bioactive
compounds from plant material. The key mechanisms are
illustrated in the accompanying Figure 7.16.
UAE induces rapid pressure changes within the extraction medium, resulting in compression and expansion.
These alternating pressure changes lead to the formation
and rapid expansion of small bubbles, known as cavitation
bubbles, within the solvent. Subsequently, during the highpressure expansion phases of the sound wave, these bubbles collapse or implode. This collapse generates localized
hotspots characterized by high temperature and pressure,
releasing energy in the form of shockwaves (Figure 7.15).
There are two types of ultrasound instruments utilized for
the extraction process: direct sonicator and indirect sonicator. The direct sonicator employs a sonicator probe to produce ultrasound directly inserted into the extracting
mixture. In contrast, the indirect sonicator allows ultrasound waves to travel through the medium. A typical UAE
setup consists of a generator, transducer, and probe. The
generator converts input electrical power into an electrical
signal, driving the transducer (Figure 7.16). The transducer, in turn, transforms the electrical signal into vibration. This vibrational motion is magnified as longitudinal
vibration at the tip of the probe, triggering cavitation
within the sample. Cavitation generates ultrasound energy,
leading to the disruption and breakdown of the sample into
Compression
– Sound pressure +
Figure 7.15 Mechanism of formation of cavitation and bursting of bubbles in UAE. Source: Kalaskar MG.
Expansion Expansion
Compression
Bubble formation from dissolved gasses and explosion of bubble
Compression
Expansion
136 7 Methods of Extraction
Ultrasound generator
Transducer
Booster horn
Probe
Sample
Direct sonicator
Figure 7.16 Schematic presentation of direct sonicator and indirect sonicator. Source: Kalaskar MG.
smaller particles. This phenomenon promotes the release
of compounds and enhances the mass transfer between the
Indirect sonicator
tion of extraction time compared to the conventional extraction process applied to Gac peel [45].
Sample
Water bath
Probe
Booster horn
Transducer
Ultrasound generator
solvent and bioactive compounds from the plant material
[3, 19, 36]. The vibrations induced by ultrasound are contingent on ultrasonic frequency and intensity, operational
temperature, time, etc. [37, 38].
UAE is a favored method for extracting heat-sensitive
compounds, exhibiting advantages, such as increased
extraction yield and energy savings [39]. Its efficacy is particularly notable in enhancing the extraction efficiency of
heat-sensitive compounds that demonstrate lower efficiency with other extraction methods [40]. These advantages contribute to a reduction in processing time and the
required amount of solvent, establishing UAE as an effective method for bioactive compounds [32, 41]. Various studies have successfully applied UAE for extracting bioactive
compounds, including phenolic compounds, isoflavone
glucosides, alkaloids, vindoline, catharanthine, vinblastine,
carnosic acid, etc., from diverse plant materials [28, 37, 42,
43]. Notably, UAE has proven successful in extracting polyphenolic compounds from red sorghum bran. Optimized
parameters for UAE in this context involved 21 minutes of
extraction time, 53% ethanol concentration, and a 52:1 mL/g
solvent-to-solid ratio, resulting in a higher extraction yield
compared to conventional solvent extraction [44]. Chuyen
et al. optimized operational parameters, focusing on extraction time and different levels of microwave and ultrasonic
powers for UAE and MAE to extract carotenoids from the
peel of Gac fruit. Significant extractions were noted when
employing MAE at 120 W for 25 minutes and UAE at 200 W
for 80 minutes on Gac peel samples. The outcomes indicate
that both MAE and UAE methodologies resulted in a reduc-
7.6.10 Microwave-assisted Extraction
Microwaves constitute a segment of the electromagnetic
spectrum, falling within the frequency range of 300 MHz
to 300 GHz and exhibiting wavelengths spanning from
1 cm to 1 m [46]. Comprising two mutually perpendicular
oscillating fields, these waves serve as carriers of both
energy and information.
MAE is a technique that utilizes microwave energy in the
form of an electromagnetic spectrum of light with a range
of 300 MHz to 300 GHz, and wavelengths of these waves
range from 1 cm to 1 m to extract compounds from medicinal herbs [46]. Microwaves are a form of electromagnetic
radiation characterized by their ability to interact with
polar molecules, particularly water, present in the herb
material. Polar molecules are exposed to microwave radiation; they continuously try to align with the alternating
electromagnetic field of the microwaves. As a result, they
rapidly rotate and generate heat through molecular friction, which increases the internal temperature of the herb
material. Consequently, the heat is generated primarily
within the moisture-containing regions or the parts of the
material with higher polar compound concentrations. This
localized and rapid heating can disrupt cell structures and
facilitate the release of target compounds into the extraction solvent. This process accelerates the extraction kinetics, reducing the extraction time required compared to
conventional methods. The process of extraction can be
efficiently used for specific targeted phytochemicals by
7. 6 Methods of Extraction 137
optimizing power level, irradiation time, and temperature
with minimum degradation [47]. Additionally, the reduced
extraction time and lower exposure to high temperatures
help preserve the integrity, quality, and bioactivity of the
extracted compounds.
In MAE, there are two main modes of operation: singlemode and multimode. These terms refer to how microwave
energy is applied during the extraction process. In singlemode MAE (SMAE), the sample receives microwave
energy through a single-mode cavity. This type of cavity
enables accurate control and directs the microwave energy
to a specific point within the sample. SMAE is known for
its focused and even distribution of microwave energy,
allowing for efficient and precise heating. It is commonly
utilized in laboratory research settings, where achieving
optimal extraction conditions requires a high level of precision and control. In multimode MAE, microwave energy is
applied through a cavity that allows the entire sample to be
exposed simultaneously. This is different from single-mode
cavities, where the energy is directed to a specific point. In
multimode systems, the distribution of microwave energy
is more widespread and less focused. These systems are
commonly employed in industrial and large-scale settings
where the emphasis is on speed and processing volume
rather than precise heating uniformity.
The selection between single-mode and multimode
MAE depends on the specific needs of the extraction process. Single-mode systems are well-suited for research
applications, offering precise control in laboratory settings.
On the other hand, multimode systems are better suited
for industrial-scale operations where efficiency and high
throughput are prioritized. The core of MAE instrumentation includes the Microwave Generator, responsible for
producing microwave energy. This generator generates
electromagnetic waves at specific frequencies tailored for
the extraction process, with adjustable power and frequency settings to meet the specific requirements of each
extraction. The Microwave Cavity serves as the chamber
where the sample and extraction solvent are exposed to
microwave energy. Single-mode cavities provide focused
energy for precise control, ideal for research applications.
In contrast, multimode cavities allow simultaneous exposure of the entire sample, making them practical for industrial-scale operations prioritizing efficiency. Temperature
Control Systems are integral, ensuring the sample is heated
to the desired temperature without causing degradation.
Some MAE systems incorporate Pressure Control Systems
to modulate pressure inside the extraction vessel. This is
particularly important for extractions involving volatile
compounds, enabling controlled conditions. The control
panel provides a user-friendly interface for setting desired
parameters (Figure 7.17).
The MAE technique boasts a faster and more uniform
heating process, resulting in an increased extraction kinetic
rate and the preservation of heat-sensitive target compounds [48, 49]. This method requires a small amount of
solvent (10–30 mL) with a wider choice of solvent types,
completing the extraction in a short period (15–30 minutes)
[50, 51]. Numerous reports in the literature underscore the
efficacy of MAE in extracting phenolic compounds, terpenoids, alkaloids, and saponins. Controlling microwave
radiation power and extraction temperature emerges as a
critical factor for the successful recovery of secondary
metabolites from plants [52].
In Pan et al. study, the extraction of polyphenols and caffeine from green tea leaves using MAE demonstrated higher
efficiency in just four minutes compared to other methods
that required 20 hours at room temperature [53]. The efficiency of MAE is strongly influenced by the dielectric constant of water and the specific properties of the sample [54].
Observations by Kumoro and Hartati revealed that increasing microwave power from 100 to 400 W led to a twofold
decrease in the extraction yield of dioscorin, an alkaloid
from gadung tubing flour. The maximum yield of 90% was
(A)
12345
panel
Control
Figure 7.17 Single-mode (A) and multimode (B) MAE apparatus. Source: Kalaskar MG.
(B)
12345
Control panel
138 7 Methods of Extraction
achieved with 100 W for 20 minutes using 85% ethanol at a
1 : 12.5 sample-to-solvent ratio. The reduction in extraction
yield with increasing microwave power was attributed to the
potential destruction of analytes at higher power ranges and
temperatures or a decrease in solubility [55].
Furthermore, microwave energy has been harnessed to
develop another innovative extraction technique known as
microwave steam distillation for extracting essential oil
from lavender [56]. Golmakani and Rezaei employed
microwave-assisted hydrodistillation to leverage microwave heating for the extraction of essential oils from thyme
species [57]. Jaradat et al. in 2018, in their study, indicated
that microwave-assisted hydrodistillation and coupled
with ultrasound leads to a reduction in total processing
time and the amount of solvent required [58].
7.6.11 Supercritical Fluid Extraction
Fusion
curve
73.8 atm
5.11 atm
Figure 7.18 Phase diagram of carbon dioxide showing the
triple point and critical points. Source: Kalaskar MG.
PHASE
Sublimation
(Not to Scale)
Pressure (atm)
SOLID
LIQUID
curve
Triple point
–56.57°C
Critical point
PHASE
GAS PHASE
Temperature (°C)
(Not to Scale)
Supercritical
uid zone
Vaporization
curve
31.1°C
SFE stands as an outstanding separation process, showing
the unique properties of supercritical fluids to serve as solvents for the extraction of distinct phytochemicals. These
fluids possess properties of both liquids and gases above
critical temperature and pressure. In the context of SFE,
the phase diagram is a crucial tool for understanding the
behavior of the supercritical fluid under different
conditions.
The phase diagram of a substance exemplifies its states
(solid, liquid, and gas) at various combinations of temperature and pressure. For SFE, the vehicle of interest is often a
gas or a liquid that is brought to a supercritical state for
enhanced extraction efficiency. The triple point represented
in the phase diagram is the combination of temperature and
pressure at which a slight change in the temperature and
pressure can convert the substance either in liquid, solid, or
gas. The critical point shown on the phase diagram signifies
the specific pairing of critical temperature and pressure, surpassing which a substance transforms into a supercritical
fluid. The region above the critical point on the phase diagram is termed the supercritical region. At this combination,
the fluid exhibits characteristics of both a gas and a liquid,
rendering it a proficient solvent suitable for the extraction of
a diverse array of compounds (Figure 7.18).
Carbon dioxide stands out as the most frequently
employed supercritical fluid (SCF), primarily attributed to
its low critical parameters (31.1 °C, 73.8 bar). Furthermore,
it boasts the advantages of being cost-effective and nontoxic. However, it does have certain limitations in terms of
polarity. This becomes particularly evident when extracting polar solutes or when strong analyte-matrix interactions are at play, where the polarity of the solvent becomes
crucial. To address these limitations, carbon dioxide fluid
is commonly blended with organic solvents, providing a
Table 7.3 List of solvents and gases with their critical
temperature and critical pressure.
Substance
Carbon dioxide 31.1 73.6
Ethane 30.54 48.8
Ethylene 28.24 50.4
Propane 36.98 42.5
Propylene 36.49 46.0
Trifluoromethane
(Fluoroform)
Chlorotrifluoromethane 30.20 38.7
Critical
Temperature (oC)
29.93 48.6
Critical Pressure
(atm)
solution to the polarity constraints. Nonetheless, various
other supercritical fluids have found application in both
commercial and developmental processes [3]. The critical
properties of some commonly utilized supercritical fluids
are as given in Table 7.3.
The SFE setup comprises a solvent reservoir (containing
carbon dioxide) and a high-pressure pump responsible for
generating pressures above the critical point and connected
to the extractor. Along with the extractor, a heating system
is aligned to ensure that the temperature remains above the
critical temperature, facilitating effective and efficient
extraction. After the completion of the extraction process,
pressure release is achieved through a pressure valve,
allowing the solvent (carbon dioxide) to revert to its original state and be separated from the extracts. The solvent, in
the form of carbon dioxide, is then recirculated and reused
in a closed-loop system [59, 60]. A schematic representation of the instrument is provided in Figure 7.19.
References 139
High pressure
pump
Gas cylinder
Figure 7.19 Schematic presentation of SFE assembly. Source: Kalaskar MG.
Co-Solvent
Heating system
SFE has been used to extract bioactive compounds from
Filter
4 Lefebvre, T., Destandau, E., and Lesellier, E. (2021).
a variety of medicinal plants, including herbs, spices, and
aromatic plants [61]. SFE has been used to extract a wide
range of bioactive compounds, including essential oils,
phenolic compounds, carotenoids, tocopherols, tocotrie-
5 Poole, C.F., (2020). Solvent selection for liquid-phase
nols, alkaloids, and other classes of chemical compounds
[62]. Ellington and his group achieved the recovery of
6 Cowan, M. M. (1999). Plant products as antimicrobial
98.6% and 98.7% for colchicine and 3-demethylcolchicine, respectively, using a carbon dioxide density of
7 Pandey A., and Tripathi, S. (2014). Concept of
0.90 g/mL (247 bar) and a carbon dioxide flux of 1.5 mL/
min. The extraction process involved the addition of 3%
methanol as a modifier and was conducted at a temperature of 35 °C with both static and dynamic phases for 25
8 Tiwari, P., Kumar, B., Kaur, M., et al. (2011).
and 30 minutes, respectively [50]. The essential oil
extracted from Piper auritum using the SFE method
exhibited a higher yield and demonstrated higher antioxi-
9 Rudraswamy, S., Godhi B.S., Shankar H.P.J., et al.
dant activity at 17.24 MPa and 40 °C. Similarly, for
Porophyllum ruderale, the extraction conducted at
17.24 MPa and 50 °C resulted in the maximum essential
oil yield, accompanied by significant antioxidant activity
10 Chanda, S.V. and Kaneria, M.J., (2012). Optimization of
[63]. SFE is a promising technique for the extraction of
bioactive compounds from medicinal plants and natural
products.
11 Mahmudati, N., Wahyono, P., and Djunaedi, D., (eds.)
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12 Marco, G.-V., Rajauria G. and Tiwari, B. (2020).
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